1. Field of the Invention
The present invention relates to the field of prostheses, and more specifically to broaches for forming the inside surface of a bone for receipt of a complimentary prosthesis.
2. Prior Art
In recent years the replacement of joints, most frequently hips, in persons having damaged, diseased or malformed joints has become more and more frequent. Since hip replacement is the most common of such operations, the same will be described herein as exemplary of the present and the developing field in general.
In the case of hip replacements, some such operations involve the replacement of the ball or proximal end of the femur with a suitable prosthesis, while other such operations further include the installation of a socket or acetabular prosthesis also. In either event however, the top of the femur is prepared for receipt of the femoral component by drilling a cylindrical hole into the femur from the proximal end thereof, and then appropriately broaching or rasping out substantially all of the remaining cancellous bone so as to shape the same to be complimentary with both the neighboring cortical bone and the adjacent portion of the prosthesis to be installed therein. In many cases, a prosthesis of a standard size is to be installed, and accordingly standard size broaches may be used. Even in these cases however, it is common to provide and use more than one broach size, such as by way of example, a slightly undersized broach for rough forming of the bone opening, and a nominal size for finishing of the opening. Given the need for different size broaches for a given implant, and the various size implants available, standard broaches are now available in a broad range of sizes.
In the prior art, bone broaches were generally fabricated from a solid piece of metal. Since the prosthesis must in effect be supported by the inside of the bone, and the inner surface of the bone at the proximal end thereof is a complicated three dimensional contour, the cutting of a broach to accurately match this three dimensional contour requires special equipment for progressively generating the cutting edges which will define the desired three dimensional contour.
In some instances wherein special problems exist such as malformed hip joints, unusually large (or small) people, certain injuries and the like, special implants must be manufactured to match the specific patient involved, typically using scan or x-ray data for the patient taken before the manufacture of the custom prosthesis and of course well before the installation operation. Obviously, a non-standard prostheses in turn requires a selection of non-standard broaches for use in preparing the bone, which non-standard broaches if manufactured from a solid piece of material are even more expensive than standard broaches. It is therefore one purpose of the present invention to reduce the cost of such broaches by simplifying the manufacturing procedure to achieve in a much less costly manner, bone broaches for the desired contours and characteristic manufactured of appropriate materials. Another purpose of the invention is to achieve a better cutting action by allowing more flexibility in the broach cutting edge design, whether the broach is of a custom or standard design. Still another purpose is to provide a broach which may be more easily and accurately inspected to verify the cutting contours at various positions thereof, again whether of a custom or standard design.